In the particle beam therapy, therapy is implemented by irradiating a charged particle beam (referred to as a particle beam, hereinafter) onto a diseased site, which is a therapy subject, so as to cause damage to diseased tissue; it is required to give a sufficient dose to the diseased tissue, which is an irradiation subject, and suppress a dose to the peripheral tissues. Accordingly, there is generated a treatment plan in order to control the irradiation dose and the irradiation coverage (referred to as an irradiation field, hereinafter) in accordance with the preliminarily measured shape of the irradiation subject. However, a treatment plan is generated under the assumption that neither the shape of an irradiation subject changes nor the position thereof is displaced; therefore, in the case where the irradiation subject is displaced due to respiration, the planned irradiation cannot be performed. Thus, with regard to an irradiation subject whose position is displaced due to respiration, there has been proposed a particle beam therapy system in which a respiratory phase is measured, and then a particle beam is irradiated onto the irradiation subject at the respiratory phase when the position and the shape are stabilized, i.e., beam irradiation is controlled through respiration synchronization (for example, refer to Patent Documents 1 and 2).
Furthermore, by focusing attention on the fact that respiration can be controlled consciously, there has been proposed a particle beam therapy system having a respiratory induction function in which the timing of expiration or inspiration is indicated so as to induce the respiration of a patient into the respiration of a predetermined period (for example, Patent Documents 3 through 6).